Hypocapnia Caused by a Cracked Water Trap

Figure 1. Cracked water trap and capnogram. After an endotracheal intubation in a male patient, a side-stream-type capnogram showed 24 mmHg of ETCO2 whereas arterial blood gas sampling revealed a PaCO2 of 44.2 mmHg. Then, a crack was found in the connector of the water trap (Figure 1A). A capnogram with the cracked water trap again showed 29 mmHg (Figure 1B) with an increase at the end of the CO2 waveform. Figure 2. Normal water trap and capnogram. A capnogram obtained with a new water trap (Figure 2A) revealed 37 mmHg (Figure 2B). Capnography is prone to certain equipment-related issues. Both normal and abnormal capnogram patterns arising from patients or from equipment should be understood for identification and resolution of the issues. The increase at the end of the CO2 waveform in the present case indicated a possible leak in the water trap. Our images clearly revealed the problem at the Luer lock connection. Cracks may occur in various stages, highlighting that care should be taken regarding deterioration of water trap connectors. In our experience, judging water trap deterioration from the CO2 waveform seemed difficult, but it may be suspected when the capnogram shows extremely low ETCO2.